Damping control of inter-area oscillations in the European power system using aggregated models

In the first part of the paper, a new approach to the reduction of large dynamic network models is presented. This method is implemented in the program package PSD and is used here in an exemplary fashion to reduce the model of the European power system to a model usable for the solution of a number of problems. In the second part, the paper describes a new damping concept of inter-area oscillations in large power systems. Additionally installed second-level damping controllers are acting on the voltage regulator reference inputs of selected generators. They are using global information about the swing profiles of the inter-area oscillations to be damped. The damping controllers are designed as a H_∞-norm optimal decentral control system based on both a topological and a frequency range decomposition of the control task. The solution is demonstrated for the reduced model of the European system. Received: 30 April 2001/Accepted: 8 June 2001     

Towards an extended power system stability: An optimized GCSC-based inter-area damping controller proposal

Due to the crucial importance of the FACTS based damping controllers in mitigation the deteriorative impacts of the power system low frequency oscillations, particularly the inter-area modes, improving the system stability margins seems indispensible. This paper proposes an optimization approach to effectively carry out the multi-machine based stabilization function of the Gate-Controlled Series Capacitor (GCSC) in providing a robust damping to the power system low frequency oscillations. It is aimed to provide a reliable damping framework by means of an optimized GCSC based supplementary damping controller. Thus, to attain the most efficient set of the damping controller parameters, Particle Swarm Optimization algorithm as a proficient optimum hunter is employed to explore for the global stabilization solution in accordance to a vast range of power system operating conditions. Moreover, as a weighty assessment, the eigenvalue analysis is taken into account as the cornerstone of the performed studies in order to investigate the damping methodology in which the unstable or lightly damped inter-area modes are scheduled to effectively shift to some predominant stability zones in the s-plane. Meanwhile, derived results through the nonlinear time domain simulation as well as two dynamic performance evaluators manifestly demonstrate the impressiveness and verify the robustness of the proposed GCSC based damping scheme in enhancing the power system stability, especially regarding to the inter-area modes.     

面向区域间振荡模式的电力系统小扰动惯量域构建

为提升低惯量电力系统的小干扰稳定性,给出保障适应新能源发展的合理惯量裕度,并明确惯量分布对于互联系统小干扰稳定性的影响规律。研究了惯量分布对系统区域间振荡模式的影响规律,构建了面向区域间振荡的电力系统小扰动惯量域(Small Signal Inertia Region, SSIR)。首先,基于部分惯量中心(Part of the Center of Inertia,PCOI)等值方法和多项式Leverrier解法,构建了等值两机系统区间振荡模式阻尼比解析式。在此基础上,依据临界阻尼比构建了计及小干扰稳定约束的惯量域。进而,对区域互联系统惯量分布和小干扰稳定性之间的联系进行解析。最后,对惯量域进行全面分析,并在新能源系统中进行了初步验证。仿真结果表明,所提出的计算方法能够实现电力系统小扰动惯量域的准确、快速构建,增强低惯量电力系统小干扰稳定性的评估和监控能力,并为新能源惯量域的构建提供理论指导。     

电力系统低频振荡实时控制

低频振荡实时控制方法将小干扰稳定在线控制策略或设定的离线策略应用于控制实际发生的低频振荡。通过小干扰稳定计算得到电网的弱阻尼模式,分别计算将各弱阻尼模式的阻尼提高到不同档位的控制措施。在电网发生低频振荡时进行在线分析,采用实测主导模式的频率筛选出候选的模式集,根据振荡中心的信息在小干扰稳定性分析中对设备进行分群,并根据设备分群信息确定与实测主导模式对应的模式,根据实测主导模式阻尼与临界安全阻尼门槛值的差值确定对应的小干扰稳定计算得到的控制措施。若没有与实测主导模式对应的模式,则从离线策略表获取辅助决策信息。最后通过自动发电控制(AGC)系统或调度员命令实施相应的控制策略。     

线路模型对仿真分析串补次同步振荡现象的影响分析

次同步振荡是一种严重威胁电力系统安全稳定运行的故障,围绕其产生机理与抑制措施,已经开展了一系列研究工作。但是,关于不同线路模型对仿真分析的影响,并未有相关文献介绍。为了探究在进行仿真分析时不同线路模型对分析结果的影响以及各自的分析适用范围,通过比较不同线路模型的阻尼水平,总结各线路模型对仿真分析串补次同步振荡现象的影响,并使用电磁暂态仿真软件ATP-EMTP进行仿真验证。验证结果表明,集中电感电阻模型、π模型、Bergeron模型的阻尼水平相当,JMarti模型所提供阻尼水平最大。在进行一般分析时,可使用集中电感电阻模型以快速得出结论;在涉及抑制装置设计的场合,应谨慎使用JMarti模型。     

双馈风电场阻尼系统次同步振荡的无功功率控制策略

引入无功-转速型传递函数,推导了双馈风电场无功功率对系统贡献的阻尼系数大小和性质的表达式,并基于分析获得的提供系统正阻尼条件,优化设计无功功率环附加阻尼控制策略抑制次同步振荡。以双馈风电场接入IEEE第一标准测试系统为例,基于Dig SILENT/Power Factory仿真平台对双馈风电场无功功率附加阻尼控制时的系统运行性能进行仿真比较。理论分析和时域仿真结果表明,推导的阻尼系数表达式以及得到的正阻尼范围条件可以有效分析双馈风电场无功功率对系统次同步振荡的作用,提出的风电场无功功率附加阻尼控制策略能在全次同步频段内提供最优正阻尼,且抑制效果优于有功功率附加PSS阻尼控制。     

FESS抑制电力系统低频振荡的机理分析

对应用飞轮储能系统(FESS)抑制电力系统低频振荡的机理进行了研究.在推导了FESS简化动态模型的基础上,采用定子磁场定向控制策略,实现FESS有功、无功的解耦控制,并分别从物理意义、基于阻尼转矩分析(DTA)的理论分析和基于等面积的图解法分析三方面详细地分析了FESS阻尼电力系统低频振荡的机理.最后,以含FESS的单...     

Suppression of DC line current oscillation of HVDC transmission system using voltage source forced commutation converter

The conventional converter used in an HVDC system requires line voltage to turn off the current flowing through a thyristor or a mercury-arc valve. Hence, the HVDC system cannot supply electric power to the system which has no ac source, such as a generator or a synchronous condenser. Thus, the HVDC system has some difficulties in operating with the weak system. The conventional solution to avoid these problems is to install large-capacity synchronous condensers which require considerable construction costs and maintenance. Another solution is the application of a forced commutation converter. The recent development of high-power and high-frequency semiconductor devices with fast gate turn-off ability (e.g., GTOs and SI thyristors) suggests the application of a voltage-source-type forced commutation converter (VSFC) to an HVDC system. To ensure the promising characteristics of the overall system, further investigation is of course necessary. The performance of dc transmission into a remote load-only system without ac source has been investigated by means of computer simulation. In many runs of a simulation program of the HVDC system using VSFC, we noticed that long sustaining oscillation of dc line current and dc voltage occurs when a large disturbance is applied. The performance is worse when series dc reactance (DCL) is installed to suppress higher harmonics of dc line current. To improve the performance of the HVDC system using VSFC, an attempt was made to install the L-R parallel damper circuit in series of dc transmission line. Simulation results when DCL and L-R damper are installed in series show that suppression of higher harmonics is as effective as the installation of DCL only, and the damping of oscillation also is substantial to improve the dynamic performance of the whole system.     

风电并网系统次同步振荡稳定性分析与控制方法研究综述

近年来,国内外多次发生并网风电场引发电力系统次同步振荡的事件,风电并网系统次同步振荡稳定性的分析与控制方法成为亟待解决的科学与工程问题。文中介绍了目前风电并网系统次同步振荡稳定性的分析方法—阻抗分析法、模式分析法和开环模式分析法,并从对振荡机理的揭示、稳定性评估结论的准确性和工程实用性三个方面进行了对比。总结归纳了风电并网系统次同步振荡负电阻和开环模式耦合机理的研究成果。从柔性交流输电系统及其附加阻尼控制器、风电机组换流器附加控制环节两个方面总结归纳了风电并网系统次同步振荡的控制方法。对目前风电并网系统次同步振荡稳定性分析与控制方法的研究中尚存在的问题以及有待突破的研究方向进行了总结和展望。     

A transient current based double line transmission system protection using fuzzy-wavelet approach in the presence of UPFC

This paper presents a wavelet fuzzy based protection scheme for a double line transmission system with unified power flow controller. The protection scheme makes use of current signals at both the ends of transmission line which are synchronized with the help of global position system clock. A wavelet based multiresolution analysis is used to find the detailed coefficients of these signals which are utilized to calculate fault index. These fault indexes are compared with a threshold value to detect and classify faults on transmission system. The approximate decomposition of the current signals is utilized to locate the fault using Fuzzy logic from their respective terminals. The proposed algorithm has been tested successfully for various faults at different locations.     

一种高压直流输电系统接地极线路保护新方法

针对目前基于信号注入的接地极线路保护方法在某些故障情况下可能出现保护拒动的问题,提出一种基于频带电压幅值积分的接地极线路保护新方法。通过仿真分析发现在高压直流输电系统接地极线路故障后其首端电压频谱会出现明显变化,基于此提出一种利用小波包分析获取接地极线路首端电压不同频带分量,以频带电压幅值积分在一段时间内的变化为保护判据的接地极线路保护方法。基于PSCAD/EMTDC软件的大量仿真结果表明,该方法能有效检测到接地极线路上的各种故障,识别准确性不受过渡电阻的影响,具有良好的应用前景。     

风火打捆外送系统次同步振荡的改进自抗扰直流附加阻尼控制

针对送端电网大规模风电接入可能加剧火电机组次同步振荡的问题,提出一种基于改进遗传算法的自抗扰附加阻尼控制方法。利用基于总体最小二乘法-旋转不变技术的信号参数估计(TLS-ESPRIT)算法对系统进行次同步振荡特性辨识,根据主模比指标选择合适的控制反馈信号,得到系统在次同步频段内各振荡模式对应的低阶传递函数;结合时间乘绝对误差积分准则(ITAE)指标与极大极小值原理确定被控系统控制目标,并利用改进遗传算法寻优确定多通道自抗扰控制器参数。在PSCAD上搭建含大规模风电的测试系统模型,仿真结果表明基于改进自抗扰控制的附加次同步阻尼控制器在送端电网多种运行方式和不同故障情况下都能有效抑制汽轮发电机组的次同步振荡,鲁棒性较强,同时低阶自抗扰控制器也具有令人满意的控制效果。     

虚拟同步发电机接入电力系统的阻尼转矩分析

针对虚拟同步发电机(VSG)控制的电压源型逆变器接入交流系统,建立含VSG的单机无穷大系统的线性化模型,分析VSG控制的新能源接入对电力系统低频振荡的影响。采用阻尼转矩分析法揭示VSG接入对电力系统机电振荡模式的影响机理,并利用DIgSILENT/PowerFactory仿真软件进行仿真验证,结果表明:VSG通过向系统中同步发电机的机电振荡环提供阻尼转矩改变系统的整体阻尼,进而影响电力系统的振荡稳定性。     

风火打捆外送系统220 kV电网次同步振荡监控策略研究

我国新疆等西北地区采用风火打捆外送系统将电能输送至用电紧缺的地区,但是由于系统网架结构相对薄弱等特点,经常发生无规律的次同步振荡。基于以往对风电场群次同步振荡监控策略的研究,当风电场群次同步振荡发生漏监时,通过对谐波产生原因及传播路径的分析,在最佳监控点220 kV电网处构架了由PMU等装置组建的监视系统,并提出分轮分级次同步振荡安全控制策略。最后,将监控策略应用于新疆麻黄沟地区,通过对振荡前后采样值波形图对比分析,验证了该策略的可行性。     

10kV扩频数字传输系统的研制

介绍了Intellon公司的线性调频收发器SSCP485，并基于该芯片和声码器AMBE－1000以及单片机研制出了一种新型的10kV扩频数字传输系统，描述了其硬件设计和软件构成，还进行了调试和性能分析。     

抑制风电-柔直外送系统次同步振荡的并联VSC型次同步阻尼控制器

风电经柔性直流输电(简称“柔直”)系统接入交流电网已经成为陆上/海上风电并网的主要方式之一,但风电与柔直系统之间存在控制相互作用引发次同步振荡的风险。为抑制此类振荡,提出一种独立于柔直系统和风电机组变流器的并联电压源变流器(VSC)型次同步阻尼控制器。该控制器使用集电线电压作为输入信号,提取信号中的振荡模态后调制其幅值、相位,然后利用并联VSC向系统注入次同步频率的电流来抑制振荡。基于复阻抗法对控制器参数进行了优化设计。仿真结果表明,所提出的控制器能在不同工况下有效抑制振荡。     

Preventive voltage control actions to securely face load evolution in power systems

One of the main aims of the System Operator (SO) is to maintain in every moment the system parameters between feasible operational margins. In certain periods of the day the load suffers fast changes which cause, specially when it tends to increase, a generalized voltage decrement and a more stressed condition for many reactive resources. In such cases, many devices may arrive to their operational limits, situation which translates into a weaker system. To avoid this negative effect the control variables should be rescheduled to maintain the normal operation conditions in the foreseeable future. This work proposes a useful tool to assist the SO when determining such actions. The main improvements are due to the implementation of a hybrid method that allows the comparison of different kinds of control variables and the inclusion of the operator background and experience in the algorithm that determines the actions. The performance of the proposed method is tested in both the IEEE 14-Bus and 118-Bus test systems.     

利用调度自动化系统动态管理35kV及以上输变电系统中的实时线损

在大量实践的基础上 ,论述了利用调度自动化系统实现输变电系统中线损的实时监测、动态管理和数据记录、整理的方法和过程 ,使线损能够快速、直观、准确地反馈给有关部门 ,及时采取相应措施 ,节能降损